Fig. 5.

Cleavage site determination of SEZ6. a Comparison of BACE1 cleavage sites in the known APP Swedish mutant, in SEZ6 and SEZ6L. Additionally, the peptide (SEZ6 pep) used for the in vitro assay is aligned. Numbers next to the N- and C-terminal amino acids of the peptide indicate the amino acid number within the sequence of the full-length protein. Amino acids at the cleavage site are shown in green. Amino acids of the transmembrane domains are in red. Domains of SEZ6 and SEZ6L are shown with indicated symbols. The most C-terminal tryptic peptide of the secreted SEZ6 ectodomain detected in our previous study is underlined in black. b Extracted ion chromatogram of full-length peptide incubated with BACE1, BACE1 plus C3 or without BACE1 showing the peaks of the two cleavage products as well as the full-length peptide. Identification of the full-length peptide (c), the N-terminal (d) and the C-terminal cleavage product (e) by fragment ion spectra. The mapped y and b fragment ions are indicated in the sequences as well as in fragment ion spectra. Neutral loss fragment ions are indicated in light blue for b and orange for y ions